Better error handling

[ffgiraldez]

Handle gracefully connectivity errors, especially when no data available offline.

Define a ComicError sealed class with 2 branches NetworkError and EmptyError

the idea is that QueryViewModel.results property now will be an LiveData<Either<ComicError,T>> instead of LiveData<T>, create a new ViewState QueryViewState.Error that contains a ComicError now on UI implementation handle it accordingly, for suggestions, for example, could be

@BindingAdapter("suggestions")
fun bindSuggestions(search: FloatingSearchView, liveData: List<Either<ComicError,String>?) = liveData?.let { 
    when (it) {
        is Left -> QuerySearchSuggestion(it.a.toHumanError())
        is Rigth -> it.b.map { QuerySearchSuggestion(it) }
    }.let { search.swapSuggestions(it) }
}

fun ComicError.toHumanError(): String = when(this) {
    is NetworkError -> "no internet conection"
    is EmptyError -> "search without results"
}

the search feature will be a more "harder" as the UI change, when a ComicError happens, the list could be hidden and display an icon with text that change based on it, as properties could be observed by more than one observer, actual @BindingAdapter will update adapter on Right values and hide the list on Left one, and create a new one to the error view that update the text/icon on Left values and hide it on Right